I am thinking about the precise formulation of the Lefschetz duality for the relative cohomology. If I understand this Wikipedia article correctly, there is an isomorphism between Hk(M,partialM) and Hn−k(M) and hence (I suppose) a non-degenerate pairing Hk(M,partialM)timesHn−k(M)rightarrowmathbbR. However, I have trouble visualizing this pairing. Let [(alpha,theta)]inHk(M,partialM) and [beta]inHn−k(M), is it then true that
left<[(alpha,theta)],[beta]right>=intMalphawedgebeta+intpartialMthetawedgebeta|partialM
or am I missing something? If unrelated to Lefschetz duality, does this pairing ever appear in topology?
I can understand how to define a pairing on the homology by counting intersections, but I really don't see how this works for cohomology. Also, a reference on Lefschetz cohomology or just analysis/topology on manifolds with boundary would be greatly appreciated!
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